CLS Research Methods & Evidence-Based Practice 3 — Questions and Answers
Question 1: Which type of study design allows a CLS to infer causation rather than mere correlation between a lubrication change and equipment outcome?
- Retrospective case study
- Cross-sectional survey
- Controlled prospective experiment (Correct answer)
- Anecdotal field report
Correct answer: Controlled prospective experiment
Controlled prospective experiments with randomization and controls are the gold standard for establishing causal relationships.
Question 2: A facility switches lubricants and bearing failures decrease. What additional evidence is needed before attributing the improvement to the lubricant change?
- A larger lubricant order
- Ruling out confounding variables such as maintenance practice changes or operating condition shifts (Correct answer)
- A positive lubricant supplier testimonial
- Repeating the same lubricant switch at a sister facility
Correct answer: Ruling out confounding variables such as maintenance practice changes or operating condition shifts
Confounding variables must be ruled out before attributing an observed improvement to a specific change in lubrication.
Question 3: In lubrication research literature, what does 'p < 0.05' signify?
- The test ran for less than 0.05 hours
- There is less than a 5% probability the results occurred by chance (Correct answer)
- The sample size was fewer than 5 specimens
- The lubricant viscosity is below 0.05 cSt
Correct answer: There is less than a 5% probability the results occurred by chance
A p-value below 0.05 means there is less than a 5% probability that the observed difference is due to random variation.
Question 4: Which organization publishes the most widely cited standardized test methods for evaluating lubricant performance properties?
- API
- ASTM International (Correct answer)
- STLE
- ISO only
Correct answer: ASTM International
ASTM International publishes the most widely used standardized test procedures for lubricant properties used globally.
Question 5: What is the primary limitation of using 'time-in-service' as the sole criterion for oil change intervals?
- It is too expensive to track
- It ignores actual lubricant condition, which can vary with load, temperature, and contamination (Correct answer)
- It requires laboratory testing
- It only applies to gear oils
Correct answer: It ignores actual lubricant condition, which can vary with load, temperature, and contamination
Time-based intervals do not account for real-world variation in lubricant degradation rates driven by operating conditions and contamination.
Question 6: A CLS reviewing a technical paper notices the sample size is n=3. What concern does this raise?
- The study cost too much
- The small sample size limits statistical power and generalizability of the conclusions (Correct answer)
- The lubricant tested must be experimental
- The paper cannot be peer-reviewed with a small sample
Correct answer: The small sample size limits statistical power and generalizability of the conclusions
A very small sample size reduces statistical power and makes it difficult to draw reliable, generalizable conclusions.
Question 7: Which concept describes the ability of a lubrication test method to produce the same result when repeated under identical conditions in the same lab?
- Reproducibility
- Repeatability (Correct answer)
- Accuracy
- Sensitivity
Correct answer: Repeatability
Repeatability measures within-laboratory precision—how consistent results are when the same method is applied under identical conditions.
CLS Research Methods & Evidence-Based Practice 3
Which type of study design allows a CLS to infer causation rather than mere correlation between a lubrication change and equipment outcome?